Method of forming post tensioned concrete liners in conduits



Nov. 28, 1967 R. E. EASTr-:RDAY

METHOD OF FORMING POST TENSIONED CONCRETE LINERS IN CONDUITS Filed June24, 1965 3 Sheets-Sheet l rillllll mmf@ FIGA

Nov. 28, 1967 R. E. EASTERDAY` 3,355,529

METHOD OF FORMING POST TENSIONED CONCRETE LINERS IN CONDUITS 3Sheets-Sheet 2 Filed June 24, 1965 fm 2/ 242 22 /fa 142A 23 2.6- 2@ l 3//v /a /M/MHVM Nov. 28, 1967 R. E. EASTERDAY. A 3,355,529

METHOD OF FORMING POST TENSIONE!) CONCRETE LINERS IN CONDUITS Filed June24, 1965 3 Sheets-Sheet 5 United States Patent O 3,355,529 METHOD FFORMING POST TENSIONE!) CNCRETE LINERS IN CONDUI'IS Robert E. Easterday,3961 Tholozan Ave., St. Louis, Mo. 63116; Joan L. Easterday, executrixwithout bond of the last will of Robert E. Easterday, deceased Fiied.lune 24, 1965, Ser. No. 466,585 Claims. (Cl. 264-32) This inventionrelates to a method of installing and post tensioninor concrete linersand more particularly to techniques for strengthening existing conduitsby providing liners of post tensioned concrete within the conduit.

Heretofore various methods and techniques have been devised for makingpost tensioned concrete structures iucluding concrete conduits. However,none of the techniques are applicable to strengthening existing conduitsby installing a post tensioned concrete liner therein. Moreover, inmaking such post tensioned concrete conduit, tensioning rods werepositioned about the outer area of the continuous concrete conduit andtensioned by tightening the tensioning rods to create compressive forcein the concrete. The prior methods are not adaptable to post tensioningconcrete structures by internal access to the existing conduit.Obviously, the concrete interior of a conduit cannot be continuous whereaccess to post tensioning rods is achieved solely by internal access tothe conduit.

The present invention provides an unique technique for forming a layerof post tensioned concrete within the existing conduit with onlyinternal access to the conduit. Briefly, the invention contemplatesinstalling post tensioning rods about the circumferential interior of anexisting conduit and forming a layer of concrete over the tensioningrods with the exception of van area for providing a post tensioningstress bearing channel or member where the ends of the post tensioningrods may be drawn together to apply tension to the rods and compressionto the concrete. The stress bearing channel or member provides acompression stress transfer member for the concrete. Moreover, theinvention contemplates providing a stress transfer plate to permitlining the Varea of an existing conduit near manhole openings with posttensioned reinforced concrete.

It is therefore an object of the invention to provide a method offorming a post tensioned concrete liner in existing conduits;

It is another object of the invention to provide a method forstrengthening existing conduits by forming a liner of post tensionedreinforced concrete within the conduit by internal access to theconduit;

It is a further object of the invention to provide a method ofreinforcing existing conduits by internal access thereto for forming apost tensioned concrete liner within said conduit;

It is `another object of the invention to provide a method of posttensioning concrete formed within existing conduit by providing posttensioning rods within the concrete liner which terminate within astress bearing member adapted to transfer compressive stress to theconcrete liner;

It is a further object of the invention to provide a method of posttensioning existing conduits by internal access thereto in areas havingentrant manholes by providing a stress transfer plate and a stressbearing channel or member with post tensioning wires extending from thestress transfer member into the stress bearing channel for applyingcompressive stress to the concrete surrounding the reinforcing wire inthe area of the entrant manholes.

These and other objects and advantages of the invention will becomeapparent from the ensuing descriptions taken in conjunction with thedrawings wherein:

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FIG. 1 illustrates a portion of an existing conduit having post tensionconcrete applied by the method of the invention;

FIG. 2 is an expanded part sectional view of the conduit of FIG. 1illustrating the stressing rod support bracket;

FIG. 3 is an expanded part sectional view of the conduit of FIG. 1illustrating the stress bearing member;

FIG. 4 is a plan view of the stress bearing member in FIG. 3;

FIG. 5 illustrates one method of tensioning the reinforcing wires andcompressing the concrete;

FIG. 6 illustrates another method of tensioning the reinforcing wiresand compressing the concrete;

FIG. 7 is a broken away portion of a stress bearing channel or memberillustrating still another method of post tensioning the reinforcingwires and compressing the concrete;

FIG. 8 is a cross sectional view taken along the line of 8 8 of FIG. 6;

FIG. 9 illustrates a section of an existing conduit in FIG. 1 having anentrant manhole for access to the conduit post tensioned by the methodof the invention;

FIG. 10 is a sectional View taken along the lines lil-10 of FIG. 9; and

FIG. 1l illustrates the stress transfer plate utilized in theinventionito permit post tensioning of the conduit in the area of anentrant manhole.

Referring now to the drawings, wherein like numerals indicate likeparts, and particularly to FIGS. l-5, an existing conduit 1 having asteel wall 2 has a reinforced concrete interior Wall, generallydesignated 3, which is installed and post tensioned in accordance withthe invention.

To facilitate installation of the reinforced concrete interior wall 3,support brackets 4 (see FIG. 2) having an angle shape are provided. Thebrackets 4 are positioned longitudinally around the internal peripheryof steel wall 2, and may be secured internally by a thin concrete layer6 coating the steel wall 2. Obviously other methods, su-ch as epoxyglue, could be used to secure brackets 4 to steel wall 2. The projectinglianges 7 of brackets 4 have a number of slots 8 which supportreinforcing rods or wires 9 circumferentiaily about and spaced fromsteel wall 2. A stress bearing channel or member 10 (see FIGS. 3 and 4),having a pair of flanges 11a and 11b, is also secured to steel wall 2 byconcrete layer 6, or epoxy glue. Flanges 11a and 11b have slots 12a and12b respectively which support the wires 9. The ends of wires 9 arepassed through bores in stressing heads 13a and 13b, and are formed withbeads 14a and 14b, respectively.

Next, concrete section 15, which forms part of interior wall 3, isformed surrounding stressing wires 9 and of the required thickness forthe desined final loading. The concrete section 15 does not till thechannel 1G. The stressing wires 9 are coated with releasing material toprevent adhesion to concrete section 15. After concrete wall 15 hascured properly, the post tensioning of wires 9 is accomplished by any ofseveral techniques. As illustrated in FIG. 5, a series of shims 16, 17and 18 of various sizes are wedged between flanges 11a and 11b and theirrespective stressing heads 13a and 13b to move the ends of wires 9towards each other placing the wires 9 in tension. The tension strain istransferred from beads 14a and 14b to stressing heads 13a and 13b,respectively, and through the shims to tianges 11a and 11b of channel10. In this manner tension stress of wires 9 creates uniform compressivestress in the concrete 15. Another means for tensioning wires 9, henceapplying compression stress to concrete 15, is illustrated in FIG. 5.The stressing heads 13a and 13b of FIG. 5 are jacked towards each otherplacing wires 9 under tension and compressing concrete 15. After thedesired tensioning of wires 9, clamping plate 19 is placed to securestressing heads 13a and 13b in the proper position. After the posttensioning has been completed, concrete ller 20 is placed within thearea around stress bearing member to complete interior wall 3 forconduit 1. Furt-her, concrete ller 20 `will prevent damage to thechannel 10.

In FlGS. 7 and 8 another method of tensioning wires 9 is illustrated. Asshown the ends 9a and 9b yof each wire 9 overlap in channel 10. Ends 9aof each wire 9 are passed through bores in frange 11a, slots 21a instressing head 21, and then through bores in stressing head 22. The ends9a are then formed with heads 14a. Likewise, the ends 9b of each wire 9are passed through bores in llange 11b, slots 22a in stressing head 22,and then through bores in stressing head 21. The ends 9b are then formedwith beads 14b. It will be understood that slots 21a and 22a instressing heads 21 and 22, respectively, may extend from either thebottom or top. A series of shims 23, 24 and 25 are positioned betweenthe ends 9a and 9b of wires 9 and intermediate stressing heads 21 and22. In this manner heads 21 and 22 are forced apart, and apply tensionto stressing wires 9, hence apply uniform compression stress to theconcrete 15.

Referring to FIGS. 9, l() and 1l, a section 3l? of conduit 1 With amanhole access housing 31 is provided with a reinforced concreteinterior wall 32, similar to interior wail 3 in the other areas ofconduit 1, surrounding the access housing that is installed and posttensioned in accordance with the invention. The section 2t? has a steelwall 33. In order to facilitate post tensioning yconcrete interior wall32, an access housing extension 34 is placed within section 3)surrounding access housing 31, and is welded in place along weld line36. After installing housing extension 34, the optional concrete layer6, as described with respect to FIGS. l-5, may be coated on the interiorof steel wall 33 to secure support brackets 4 and stress bearing channel16 thereto. Next, a curved plate 37 having a central opening 3S ispositioned around extension 34, and is welded in place. The curved plate37 has a series of slots 39 which communicate with enlarged openings4t?. Enlarged heads 41 at one end of stressing wires 9 seat in enlargedopenings 4t) with wires 9 in slots 39. Of course, the other ends ofwires 9, although not illustrated, extend into channel 16, The wires 9are supported by support brackets 4 positioned around the interior ofsteel wall 33, similarly as with respect to steel wall 2. Next, concretesection 15, forming part of interior wall 32, is provided surroundingstressing wires 9 exteriorly of housing extension 34 and channel 19.When cured, concrete section is post tensioned by any of the techniquesmentioned heretofore. The interior wall 32. is completed by placingconcrete filler 26 within the area of channel 10.

From the foregoing it will be appreciated that appliycants methodcontemplates supporting stressing wires around the interior of anexisting conduit which wires terminate in stress bearing channels ormembers, covering the stressing wires with a concrete wall exteriorly ofthe stress bearing channel or members, and thereafter post tensioningthe wires to compress the concrete wall. Moreover, applicants methodpermits transfer of post tensioning stress past manhole access housingsin the conduit. By this technique, it will be appreciated thatapplicants method permits post tensioning to provide a reinforcedconcrete interior wall within an existing conduit solely by internalaccess thereto.

It will be appreciated that various modifications and changes toapplicants techniques will be readily apparent to those skilled in theart, and therefore all such modications and changes are deemed to bewithin the scope of the invention as defined by the appended claims.

What is claimed is:

1. A method of forming post tensioned concrete liners in existingconduit comprising the steps of applying a thin coating of cementitiousmaterial to the internal surface of the conduit securing a stressbearing member by said cementitious material to said conduit, supportingstressing wires around the interior of said conduit With the endsthereof extending into said stress bearing member, forming a layer ofconcrete around said stressing wires exteriorly of said bearing member,and post tensioning said wires.

2. A method of forming post tensioned concrete liners in existingconduit comprising the steps of applying a thin coating of cementitiousmaterial to the internal surface of the conduit securing a stressbearing member by said cementitious material to said conduit, supportingstressing wires peripherally around the interior of said conduit withthe ends of said wires terminating in said stress bearing member,forming a layer of concrete around said stressing wires exteriorly ofsaid bearing member, and forcing the ends of said wire in opposeddirections to post tension said wires.

3. A method of forming post tensioned concrete liners in conduit membersby internal access thereto comprising the steps of applying a thincoating of cementitious material to the internal surface of the conduitsecuring a stress bearing member by said cementitious material to saidconduit, extending stressing wires peripherally around the interior ofsaid conduit with the ends of the stressing wires terminating in saidstress bearing member, forming a layer of concrete around said stressingwires exteriorly of said bearing member, and forcing the ends of saidwires in opposed directions to apply compressive force to said layer ofconcrete.

4. A method of forming post tensioned concrete liners in conduit membersby internal access thereto comprising the steps of applying a thincoating of cementitious material to the internal surface of the conduitsecuring a stress bearin(y member by said cementitious material to saidconduit, extending stressing wires circumferentially around the interiorof said conduit with the ends of the stressing wires overlappinglyterminating in said stress bearing member, forming a layer of concretearound said stressing wires exteriorly of said bearing member, andforcing the ends of said wires away from each other to apply compressiveforce to said layer of concrete.

5. A method of forming post tensioned concrete liners in existingconduit by internal access to the conduit comprising the steps ofapplying a thin coating of cementitious material to the internal surfaceof the conduit securing a stress bearing member by said cementitiousmaterial to said conduit, securing support members within said conduit,placing stressing wires around the interior of said conduit supported bysaid support members with the ends of the stressing wires extending intosaid bearing member, forming a layer of concrete over said stressingwires exteriorly of said bearing member, drawing the ends of the wirestoward each other in said stress bearing member to post tension saidwires, and thereafter filling said stress bearing member with a layer ofconcrete.

6. A method of forming post tensioned concrete liners in existingconduit by internal access to the conduit comprising the steps ofapplying a thin coating of cementitious material to the internal surfaceof the conduit securing a stress bearing member by said cementitiousmaterial to said conduit, securing support members within said conduit,placing stressing wires around the interior of said conduit supported bysaid support members with the ends of the stressing wires overlappinglyextending into said bearing member, forming a layer of concrete oversaid stressing wires exteriorly of said bearing member, forcing the endsof the wires away from each other interiorly of said stress bearingmember to post tension said wires, and thereafter filling said stressbearing member with a layer of concrete.

7. The method of forming post tensioned concrete liners in existingconduits having an entrant access opening comprising the steps ofapplying a thin coating of cementitious material to the internal surfaceof the conduit positioning a stress transfer member Within said accessopening, securing a stress bearing member by said cementitious materialto said conduit peripherally aligned with said stress transfer member,supporting stressing wires around the interior of said conduitintermediate each side of said stress transfer member and said stressbearing member with one of the ends of the stressing Wires secured tosaid stress transfer member and the other ends of the stressing Wiresextending into said stress bearing member, forming a layer of concretearound said stressing Wires exteriorly of said stress transfer memberand said stress bearing member, and post tensioning said stressing wiresto apply compressive force to said concrete liners.

8. The method of forming post tensioned concrete liners in existingconduits having an entrant access opening comprising the steps ofapplying a thin coating of cementitious material to the internal surfaceof the conduit positioning a stress transfer member Within said accessopening, securing a stress bearing member by said cementitious materialto said conduit peripherally aligned with said stress transfer member,supporting first stressing Wires around the interior of said conduitintermediate said stress transfer member and said stress bearing memberwith one of the ends of the stressing wires secured to said stresstransfer member and the other ends of the stressing wires extending intosaid stress bearing member, forming a layer of concrete around saidstressing Wires exteriorly of said stress transfer member and saidstress bearing member, post tensioning said stressing wires to applycompressive force to said concrete liners, and thereafter filling saidstress bearing member with a layer of concrete.

9. A method of forming post tensioned concrete liners in an existingconduit having an entrant access opening comprising the steps ofapplying a thin coating of cementitious material to the internal surfaceof the conduit positioning a stress transfer member Within said accessopening, securing a stress bearing member by said cementitious materialto said conduit peripherally aligned with said stress transfer member,supporting a first series of stressing wires around the interior of saidconduit from one side of said stress transfer member to one side of saidstress bearing member with one end of the first series of stressingWires secured to said one side of said stress transfer member and theother ends of the first series of stressing wires extending into saidone side of stress bearing member, supporting a Second series ofstressing Wires around the interior of said conduit from the other sideof said stress transfer member to the other side of said stress bearingmember with one end of the second series of stressing wires secured tothe other side of said stress transfer member and the other ends of saidsecond series of stressing Wires extending into said other side of saidstress bearing member, forming a layer of concrete around said firstseries of stressing wires and said second series of stressing wireexteriorly of said stres transfer member and said stress bearing member,and forcing said other ends of said first series of said stressing wiresand said other ends of said second series of stressing Wires in opposeddirections to post tension said first series of stressing Wires and saidsecond series of stressing Wires.

10. A method of forming post tensioned concrete liners in an existingconduit having an entrant access opening comprising the steps ofapplying a thin coating of cementitious material to the internal surfaceof the conduit positioning a stress transfer member Within said accessopening, securing a stress bearing member by said cementitious materialto said conduit peripherally aligned With said stress transfer member,supporting a first series of stressing Wires around the interior of saidconduit from one side of said stress transfer member to one side of saidstress bearing member with one end of the first series of stressingwires secured to said one side of said stress transfer member and theother ends of the first series of stressing Wires extending into saidone side of said stress bearing member, supporting a second series ofstressing Wires around the interior of said conduit from the other sideof said stress transfer member to the other side of said stress bearingmember with one end of the second series of stressing wires secured tothe other side of said stress transfer member and the other ends of saidsecond series of stressing Wires extending into said other side of saidStress bearing member, forming a layer of concrete around said firstseries of stressing Wires and said second series of stressing Wiresexteriorly of said stress transfer member and said stress bearingmember, forcing said other ends of said first series of said stressingwires and said other ends of said second series of stressing Wires inopposed directions to post tension said first series of stressing Wiresand said second series of stressing Wires, and thereafter filling saidbearing member with a layer of concrete.

References Cited UNITED STATES PATENTS 1,818,524 8/l93l HeWett 264-2282,315,895 4/1943 Crom 264-228 X 2,319,105 5/1943 Billner 264-228 XROBERT F. WHITE, Primary Examiner.

J. A. FINLAYSON, Assistant Examiner.

1. A METHOD OF FORMING POST TENSIONED CONCRETE LINERS IN EXISTINGCONDUIT COMPRISING THE STEPS OF APPLYING A THIN COATING OF CEMENTITIOUSMATERIAL TO THE INTERNAL SURFACE OF THE CONDUIT SECURING A STRESSBEARING MEMBER BY SAID CEMENTITIOUS MATERIAL TO SAID CONDUIT, SUPPORTINGSTRESSING WIERES AROUND THE INTERIOR OF SAID CONDUIT WITH THE ENDSTHEREOF EXTENDING INTO SAID STRESS BEARING MEMBER, FORMING A LAYER OFCONCRETE AROUND SAID STRESSING